V/Q Scan

Thyroid Treatment

Low dose therapy for benign thyroid disease

1. Alternative methods of treatment

   • Surgery—Rarely performed except in children, patients with very large goiters resulting in respiratory compromise, patients who refuse I-131 therapy, and in those with suspicion of thyroid cancer. Complications of surgery include hemorrhage, infection, hypocalcemia, vocal cord paralysis, scarring, and recurrent hyperthyroidism.

   • Anti-thyroid medications (PTU, methimazole)- side effects include rash, urticaria, arthralgia, transient leukopenia, hepatitis. Patients often with have a trial of 6-12 months to determine if medical therapy is a viable option.

2. Radioactive I-131—beta emission for therapy and gamma emission for imaging.

   • Easy PO administration, effective (most patients require only 1 dose), safe.

   • Early side effects include pain (thyroiditis), mild nausea, transient worsening of hyperthyroid symptoms. Thyroid storm is a very rare potential side effect.

   • Late side effects—Hypothyroidism is expected.

3. Miscellaneous

   • Expect 1-2 months before symptomatic improvement. During this time anti-thyroid medications can be resumed. Beta blockers can be used for tachycardia.

   • Do not retreat before 6 months have elapsed.

   • No significantly increased carcinogenic risk with doses utilized for benign thyroid disease.

   • Fertility is not affected. It is recommended that patients are counseled to not become pregnant for the first 6 months after therapy.

   • Must ensure that the patient is not pregnant at the time of therapy.

4. Radiation safety

   • Most excreted activity is via the kidneys and excretory system. Flush 2 times after voiding.

   • For 3 days, maintain a 6’ distance from others. Sleep in own bed, etc

   • At the conclusion of 3 days, wash bedsheets clothing, towels, etc.

High dose treatment for thyroid cancer.

1. Optimal treatment of well differentiated thyroid cancer includes thyroidectomy, I-131 ablation, and subsequent thyroid hormone supplementation.

2. Prognosis with optimal treatment is excellent, >95% 5-year survival.

3. Rationale for I-131

   • Destruction of thyroid remnant—allows for optimal follow up with thyroglobulin and future I-131 imaging.

   • Treatment of residual neoplasm.

4. Side effects

   • Approximately 25% will experience nausea and/or headache to some degree.

   • Sialadenitis. Best mitigation steps are to stay hydrated and eat sour candy/lemons. Start the morning after therapy dose is ingested. Continue for at least 48 hours.

   • Metallic taste in mouth. Transient taste alterations.

   • Neck pain is uncommon. Dependent on volume of post operative thyroid remnant.

   • Transient bone marrow suppression (6-8 weeks after treatment)- uncommon at doses less than 200 mCi.

   • Birth defects—must ensure that the patient is not pregnant.

   • Must ensure that the patient is not lactating. Recommend cessation of breast feeding, optimally 1-3 months prior to treatment. Risk of radiation effects to breast increase in lactating women and iodine could be passed to infants in breast milk.

5. Potential late side effects

   • Leukemia—Rare. Especially rare in patient less than 50 y/o and cumulative doses <800 mCi. Patients receiving multiple large doses in a short time frame are at greatest risk.

   • Radiation fibrosis is a potential risk for patients with diffuse pulmonary metastasis at the time of high dose therapy. Only reported in patients with deposition of >80 mCi in lungs.

   • Infertility—not reported in women. Potential effect in males with repeated large doses.

6. Follow-up

   • Whole body imaging at 7 days after treatment

   • Clinical follow up with thyroglobulin.

   • Repeat imaging in 1 year depending on thyroglobulin levels.

7. Radiation safety

   • Goal is to prevent more than 500 mrad exposure to non-patients.

   • Most excreted activity is via the kidneys and excretory system. Flush 2 times after voiding x 3 days.

   • Avoid strenuous work, workouts, etc to minimize sweating.

   • For 3 days, maintain a 6’ distance from others. Sleep in own bed, etc.

   • At the conclusion of 3 days, wash bedsheets, clothing, towels, etc. Switch to a new toothbrush.

   • Avoid allowing pets to lick your skin or sit on your person.

   • Avoid sexual contact for 1 week.

   • Avoid becoming pregnant until at least one year and initial follow up is completed. If a retreatment is needed, a pregnancy and newborn will prolong time before treatment could be initiated.